A larger version of the 18th century solar microscope, they were first freestanding, a design analogous to picture-taking cameras but with the relative position of negative and lens reversed so that sunlight shone through the glass plate to be projected onto photo-sensitive paper inside the instrument. Solar cameras, introduced in the late 1850s, and ancestors of the darkroom enlarger, were necessary because of the low light sensitivity of albumen and calotype materials used.
David Acheson Woodward's 1857 'solar enlarging camera' addressed that problem by tapping the brightest light-source then available – the Sun – with mirrors and a condenser. Achille Quinet's invention of 1852 used artificial light, but was inefficient, requiring very extended exposures. The advent of collodion negatives on glass in the 1850s made enlargement more practical. In 1848 Talbot recommended to fellow photographer Thomas Malon the enlarging camera made by Thomas Ross of lens manufacturers Ross, Andrew & Thomas. In June 1843 Henry Fox Talbot in his patent for an enlarger for his calotype process which produced a paper negative, mentions that using lenses it is possible to produce a large negative from a smaller, so having made such enlargements has a priority claim to be the inventor of a system for making an enlarged print from a negative, though it did not go into production and was not practical given the lengthy exposures required. This method will probably contribute very much to the practice of the art" In March 1843 Americans Wolcott and Johnson patented a means of copying and enlarging daguerreotypes. These are subsequently enlarged to the required size in a larger camera on a rigid stand. Eder credits the first mention of enlargements after the announcement of the daguerreotype (unique images on metal plates) to John William Draper who in 1840, during, wrote prophetically in the American Repository of Arts "Exposures are made with a very small camera on very small plates. Davy in which he described their experiments with the photosensitivity of silver nitrate. In June 1802 Davy published in the first issue of the Journals of the Royal Institution of Great Britain his An Account of a Method of Copying Paintings upon Glass, and of Making Profiles, by the Agency of Light upon Nitrate of Silver. Josef Maria Eder, in his History of Photography attributes the invention of photographic enlargement to Humphry Davy who realised the idea of using a solar microscope to project images onto sensitised paper. Salted paper print from a calotype paper negative, the left component of a panoramic pair of views, 1846. Staff at William Henry Fox Talbot's commercial calotype establishment in Reading, Berkshire.
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